Sometime before the battle the Yuuzhan Vong had secretly established a base on the uninhabitable planet Dibrook. They also placed a Yammosk under the surface.
The Yuuzhan Vong appeared out of nowhere to attack the Dibrook Space Station. Commander Bylsma ordered his starfighters to fight back, even though the Yuuzhan Vong had stripped the shields of both the station and the fighters. Even though the New Republic's ship outnumbered the Yuuzhan Vong's they had a hard time fighting without shields. Some of the refugees living on the station were captured during the battle and brought to the surface on Dibrook, where the Yuuzhan Vong had established a base.
The sudden appearance of the Heart of Artorias, a captured Yuuzhan Vong slaveship, caused some confusion amongst the New Republic command, but when it started firing on the Yuuzhan Vong they quickly realized it was on their side and they ordered their starfighters not to fire on it. With the help of the Heart of Artorias the Yuuzhan Vong were soon fought off.
The Heart of Artorias connected with the Dibrook Space Station to take on refugees from damaged sections. The ship's commander, Kaye Galfridian, learned that some refugees had been taken to Dibrook by the Yuuzhan Vong. And with help from the station's commander she organized a rescue mission.